For the control of automatic gearboxes, use is made of electronic controllers which are either arranged in the interior of the gearbox housing (integrated control unit) or are mounted onto the gearbox housing from the outside (attachment control unit).
Attachment control units can have the advantage over integrated control units that they are subjected to lower temperatures and can thus be designed to be cheaper. It can however be a disadvantage that attachment control units take up a very large amount of structural space in the engine bay, and the outlay for leading electrical lines from the outside to the sensors and actuators situated in the interior of the gearbox is higher.
Integrated control units are generally constructed as so-called electronic control modules and may comprise an electronic circuit or an electronics component (“transmission control unit”, TCU), sensors, at least one plug connection for connecting to the vehicle wiring loom, and electrical interfaces for the activation of actuators.